1. Field of the Invention
This invention relates to a device for harvesting plants that are deeply and/or complexly rooted in the ground, and more particularly to a device for harvesting tree seedlings which are intended for replanting in the ground to undergo further growth thereafter. Specifically, the present invention relates to an improved tree seedling harvester which increases the efficiency and effectiveness of the harvesting operation and results in harvested tree seedlings which are cleaner and undamaged.
2. Description of the Prior Art
Plants which have deep and/or complex root systems are not readily susceptible to machine harvesting due to the problem of separating the roots of the plants from the body of earth contiguous thereto. This problem is particularly acute when the plants are intended for replanting to undergo further growth, as in the case of nursery grown tree seedlings intended for replanting on a tree farm or for reforestation.
Prior to the invention disclosed in U.S. Pat. No. 3,693,721, issued on Sept. 26, 1972, to Eugene W. Arnold et al, most tree seedlings had been harvested by hand for the reason that techniques were unavailable whereby the seedlings could be machine harvested without unduly damaging the plants, particularly the root structures. The tree seedling harvester disclosed in the aforementioned patent, the contents of which are herewith specifically incorporated by reference, considerably improved the methods and techniques for machine harvesting tree seedlings. However, certain inadequacies and problems with the disclosed harvester were eventually discovered. One such problem was that too much earth adhered to the roots of the seedlings as they were lifted from the ground, thereby requiring considerable agitation to the root structures to remove the earth. Such excess agitation can cause damage to the root system. Another problem was that the mechanism utilized to shake or agitate the roots caused considerable vibration in the harvester. An additional inadequacy was that the gripper belts which lift the tree seedlings from the ground required too much "squeeze" force against the stems of the seedlings in order to hold them between the belts, and this can also damage the seedlings. Finally, the design of the sheaves which carry the gripper belts was such that replacement of an entire sheave structure was necessary whenever the bearings therein became worn, and this is very time consuming and costly.